Drop-out fuse



Aug. 4, V1942. A. RAMSEY Erm..

DROPOUT FUSE Filed Dec. 14, 1936 4 Sheets-Sheet l Aug. 4, 1942'. A. RAMsx-:Y Erm.

nRoPoUT Fuss Filed nec. 14, 1956 4 Sheets-Sheet 2 All@ 4. 1942- A. RAMsEY E-rAL 2,292,341

' DROPOUT FUSE Filed DGO. 14, 1936 4 Sheets-Sheet 3 Aug. 4, 1942. A. RAMsEY Erm.

DROPOUT FUSE -Filed Dec. 14, 1936 4 Sheets-Sheet 4 Patented Aug. 4, 1942 DROP-OUT Fosa Allan Ramsey, Evanston, and Sigurd I. Lindell and Anthony Van Ryan, Chicago, Ill., assignors to Schweitzer & Conrad, Inc., Chicago, Ill., a

corporation of Delaware Application December 14, 1986, Serial No. 115,690

41 Claims.

In the copending application of Allan Ramsey,`

one of the joint inventors of the invention disclosed herein, Serial No. '559,846, led August 28, 1931, and assigned to the assignee of this application, now Patent No. 2,091,452, a fuse device of the expulsion type is disclosed which is mounted detachably on the cover of a box that is removably hinged at its lower end to close the front side of the box. On the rear wall of the box stationary terminals are provided to which the circuit connections may be made. The stationary terminals are in the form of blocks the opposite sides of which are engaged by flexible contact fingers in the form of spring wires that are located on and carried by each end of the fuse device and constitute its terminals. This construction provides simple rigid terminals in lthe box and facilitates removal of those parts that are most likely to require adjustment and replacement and leaves aminimum of live parts in the box when the cover is open. kWith a view to limiting the movement toward each other of the spring wire ngerswhen the device is in the open position, stop members are provided which limit the movement of the contact ngers so that their contact engaging portions will be positioned slightly within the path of relative movement willi the stationary terminals. When the device is operated to the closed position, it is only necessary to move the contact iingers slightly out of engagement with the stop mem- -bers and the full resiliency of the lingers will then be available toprovide the relatively high contact pressure for each oi the small area contact engaging portions.

The object of the present invention, generally stated, is to embody the principles of contact construction disclosed in said copending application in a fuse device of the dropout type.

An important object of the invention is to provide, in a dropout fuse device of the rotary type, interacting contact fingers and jaws which serve not only as a circuit connection but also as a means for restraining the fuse device from rotation to the open position.

Another important object of the invention is to provide 'for prestreming a pair of contact fingers carried by a fuse device of the dropout type by biasing them apart and limiting the movement apart to position them slightly within vthe path of relative movement with a cooperating stationary contact member comprising a pair of upstanding substantially inflexible arms.

Still another important object of the invention is to slidably mount a fuse device having a pair of prestressed contact fingers in a hinge member attached to the cover of a box and to permitl first a translatory movement of the fuse device on blowing of its fusible element to effect separation of the fuse terminals and interruption of the arc during the initial part of the translatory movement and to disengage the c ontact fingers by the completion of the translatory movement and then to permit a rotary movement of the fuse device, hinge member and cover to introduce an air gap in the circuit in addition to that provided by the blowing of the fusible element.

Another object of the invention is to provide a mechanical barrier of insulating material between the lower contact clip and the cover hinge support to prevent accidental contact between the clip and support,

Still another object of the invention is to facilitate the sliding of a fuse device having prestressed contact ngers on blowing of its fusible element from engagement with a terminal clip and to release it for rotation to open position.

A still further object of the invention is to permit a limited movement of the fuse tube of a dropout fuse device relative to its support for the purpose of separating the terminals of the fuse link and extinguishing the arc without releasing the catch that holds the fuse device against rotary movement.

Other objects of the invention will, in part, be obvious and in part appear hereinafter.

The invention, accordingly, is disclosed in the embodiment thereof shown in the accompanying drawings, and it comprises the features of construction, combination of elements and arrangement oi parts which will be exemplied in the construction hereinafter set forth, and the scope of the application of which will be indicated in the appended claims.

For a more complete understanding of the nature and scope of the invention, reference may be had to the following detailed description taken in connection with the accompanying drawings, in which:

Figure 1 is a view, in side elevation, of the novel dropout fuse device, illustrating how it may be mounted on a cross-arm;

Figure 2 is a view, partly in side elevation and partly in section, showing the details of construction of the dropout fuse device;

Figure 3 is a bottom plan view of the device illustrated in Figure 2;`

Figure 4 is a sectional view taken generally along the line 4-4 of Figure 2;

Figure 5 is a detail sectional view taken generally along the line 5-5 of Figure 2;

Figure 6 is a sectional view showing the details of construction of the fuse tube, fuse link and the associated operating parts and contact fingers;

Figure '7 is a fragmentary view, in side elevation, of the lower end of the fuse tube and the hinge member in which it is slidably mounted;

Figure 8 is a view, in top plan, of a spacer that may be optionally used to prevent the cover of the box from rotating when the fuse device blows;

Figure 9 is a detail sectional view showing, at an enlarged scale, the details of construction of one of the flexible contact fingers that is carried by the upper end of the fuse tube; and

Figures 10 and 11 are views, similar to Figures 4 and 5, showing alternate forms of contact fingers.

Referring rst to Figure 1 of the drawings, it will be observed that the reference character I0 designates, generally, a fuse device of the dropout type which comprises a box II, formed preferably of porcelain, and a cover I2, formed preferably of a suitable molded insulating material, and having integrally formed therewith an eye I3 to permit operation of the cover from a remote position by a hook stick. The cover I2 is arranged to be hingedly mounted with respect to the box I I for movement from the closed position to the alternate position shown by the broken lines.

The box II is provided with a rearwardly extending L-shaped bracket I4 which may be secured by a suitable clamp, shown generally at I5, to a cross-arm I5 in the customary and well known manner. In some applications it may be desirable to mount the box I I substantially horizontally rather than in the substantially vertical position, as shown in Figure ll The cover I2 would then open downwardly and would not expose the interior of the box II directly to the weather on blowing of the fusible element. As will hereinafter appear, the cover I2 is so hinged to the box II that it will not be released from the box II even though it is placed in the horizontal position.

As illustrated more clearly in Figure 2 of the drawings, a sleeve I9, formed preferably by a single metallic casting, is secured by screws 20 to the inside of the lower end of the cover I2. 'I'he sleeve I9 is provided at its lower end with hook-shaped portions 2I on opposite sides thereof for mounting on trunnions 22 that extend inwardly from the outwardly extending arms 23 of a fulcrum member 24. The inner end of the fulcrum member 24 may be secured by screws 25 to an insert 23 which is cemented into a suitable recess in the rear wall 21 of the box III, as shown. It will be noted that the ends 23 of the hook-shaped portions 2I encircle the trunnions 22 for a substantial portion thereof and to such an extent that they will not become detached even though the box II is mounted in the substantial horizontal position, as indicated hereinbefore.

Upper -and lower stationary terminals 32 and 33 are cemented into suitable recesses in the rear wall 21 and they are respectively provided' with longitudinally extending apertures 34 and 35 in which the circuit conductors may be positioned and secured by set screws 35 and 31. The

apertures 34 and 35 are aligned with apertures in the side walls of the box II so that the circuit conductors may be readily introduced as will be readily understood. Upper and lower stationary contact clips 33 and 39 are mounted on the upper and lower stationary terminals 32 and 33 by screws 4Il and 4I and they are provided, respectively, with inwardly extending shoulders 42 (Figure 4) and 43 (Figure 5) and out flared ends 44 and 45. It will be noted that the contact clips 38 and 39 are formed of relatively thick material, preferably copper strap, so that the outwardly extending arms carrying the inwardly projecting shoulders 42 and 43 are substantially inflexible.

With a view to preventing accidental contact between the lower stationary terminal 33 and the fulcrum member 24 when the cover I2 is open, the rear wall 21 is provided with an integrally formed inwardly extending barrier 49. In this manner the fulcrum member 24 is more effectively insulated from the stationary terminal 33 than would be the case if the barrier 49 were omitted. In like manner a barrier 59 is interposed 4between the terminals 32 and 33 to increase the electrical creepage distance therebetween and to reduce as far as possible the likelihood of a flashover. It will be understood that the barriers 49 and 50 are not only integrally formed with the rear wall 21 but also that they are integrally formed with the side walls of the box II to act as mechanical reinforcement therefor.

The cover I2 is provided with an integrally formed inwardly extending shoulder 5I having a transverse aperture 52 therein for slidably mounting a fuse device that is indicated generally at 53. The shoulder 5I acts not only as a guide for the fuse device 53 but also it serves to limit the downward movement thereof on blowing of its fusible element as will be presently apparent.

The fuse device 53, Figure 6, comprises a fuse tube 54 that is formed of a suitable insulating material and is provided with a fiber liner 55. A fusible element, designated generally by the reference character 56, is positioned inside of the fiber liner 55 and it has a flexible conductor 51 extending outwardly therefrom through the bore of the ber liner 55. The fusible element 55 may be of any suitable type the terminals ofwhich will be separated on blowing of a calibrated conductor when the current flowing therethrough exceeds a predetermined value. For example, it may comprise a tube 56a of insulating material in which are positioned a strain wire 56h and a fuse wire 56e, preferably formed of silver, that are fastened at one end to the flexible conductor 51 and at the other end to a head 58. 'I'he head 59 not only serves as a connection to a threaded ferrule 59 but also it positions the fusible element 56 in the upper end of the bore of the fiber liner 55. A threaded cap 60 is mounted on the threaded end of the ferrule 59 to cover the same, The ferrule 59 is secured to the upper end of the fuse tube 54 by transversely extending pins 6| that are more clearly shown in Figure 4. Before assembly of the ferrule 59 on the fuse tube 54 the holes for the pins 6I are drilled therein on the opposite sides. After the ferrule 59 has been positioned on the upper end of the fuse tube 54 a drill is run through the previously drilled openings in the ferrule 59 and through the tube 54 after which the pins 5I are driven into tight fitting relationship therein. In this manner the ferrule 59 is securely held to the upper end of the fuse tube 54 to prevent the assembly from being blown off of the upper end of the fuse tube 54 when the fuse device 66 blows under short circuit conditions. In such case a considerable pressure is developed in the upper end of the fuse tube 54 and. unless a sturdy construction is provided for closing the upper end, the gases formed thereby may be blown out at this end with the result that damage to the box II and cover I2 and the contact members housed thereby in the upper end may be damaged.

At the lower end of the fuse tube 54 a ferrule 62 is secured by suitable means. 'Ihe fuse tube 64 is slidably mounted in the sleeve I9, as illustrated more clearly in Figure 6 of the drawings, and a coil spring\64 is interposed between the upper side of the ferrule 62 and the underside of a recessed aperture in the sleeve I9 to bias the fuse device 53 downwardly. The ferrule 62 is provided with a pair of integrally formed arms 65 that engage the upper sides of flanges 66 integrally formed with a lever or ipper 66a that is hinged on a 'pin 61 which extends transversely between a pair of ears 68 that are formed integrally with the sleeve I9. The flanges 66 insure the proper positioning of the arms 65 relative to the lever or flipper 66a on refusing. A connector stud 69 is secured in an inclined wall of the sleeve I9 and it is longitudinally slotted to provide for slidably positioning therein a spacer 10 that is movable with a nut 1I that is threaded on the connector 69. The spacer 10 is formed by bending to the desired shape a thin narrow strip of copper strap. The flexible lead 51 from the fusible element 56 is positioned in a relatively deep groove 12in the underside of the lever 66a and then is drawn through the longitudinal slot in the connector 69 until the various parts assume the relative positions shown in Figure 6 of the drawings. The nut 1I is then tightened to secure the end of the flexible lead 51 in position.

It will be observed that the arm 65 engages the upper surfaces of the flanges 66 in close proximity to the pin 61 about which the lever or flipper 66a is fulcrumed. In this manner the fusible element 56 has a considerable mechanical advantage over the biasing force of the spring 64. For the same reason, when the fusible element 56 blows, the terminals thereof between which the arc is drawn are separated at a very rapid rate because of the fact that the left hand end of the lever or flipper 66a. moves at a high speed as compared to the speed of movement of the fuse tube 54 in the sleeve I9. It will be understood that it is desirable to separate the terminals of the fusible element 56 at a high speed in order to extinguish the arc drawn therebetween as soon as possible. The relatively powerful spring 64 is arranged to operate at a mechanical advantage as described in order to separate the terminals with a minimum of delay and at the same time to move the fuse tube 54 to separate it from the stationary terminal 32 as will be presently apparent.

The construction of the lever or flipper 66a is important in order to make certain that it functions properly on blowing of the fusible element 56. The deep groove 12 is provided in its under surface in order to insure that the lower end of the flexible lead 51 moves together therewith rather than possibly slipping off on operation of the fusible element 56. Since the lever or flipper 66a must be moved onblowing of the fusible element 56 in order to separate its terminal, the

inertia of the parts that must be moved should element 56 may take place.

the sleeve I9 rather than being positioned on the lever or flipper 66a. In this construction it is only necessary to accelerate the lever or flipper 66a and the flexible lead 51 in separating the terminals of the fusible element 56. It will be observed that the lever or flipper 66a is positloned substantially at right angles to the longitudinal axis of the bore of the fuse tube 54 or the ber liner 55 therein. It will also be noted that the lower end of this bore is substantially unobstructed so that the free egress of the gases that are evolved on the blowing of the fusible With this positioning of the lever or flipper 66a the flexible lead 51 is drawn directly outwardly of the bore during the initial movement rather than being drawn over the lower edge of the bore. In this manner the friction force that must be overcome during this initial movement is negligible and consequently the terminals of the fusible element 56 are rapidly separated. In Figure 'I of the drawings the relative positions of the various parts after the fusible element 56 has blown are illustrated.

In order to electrically connect the fuse device 53 across the stationary terminals 32 and 33 prestressed contact members 16 and 11 are provided for engaging between the outwardly extending jaws of the contact clips 38 and 39. The contact members 16 serve to hold the fuse device 53 and the cover I2 on which it is slidably mounted in operative position while the contact members 11 are arranged to bias the fuse device 53 and cover I2 to the open position when the fusible element 56 blows.

The details of construction of the prestressed contact member 'i6 are more clearly illustrated in Figure 4 of the drawings. As there shown it comprises a pair of spring contact ngers 18 that are formed by a substantially U-shaped construction, the common portion being flattened and secured as by rivets 8U to a correspondingly flattened portion of the upper ferrule 59. The spring fingers 'I8 are fastened to the side of the ferrule 59 remote from the contact clip 38 in order to provide a maximum resiliency therein with a minimum of depth Aof box II. Each of the contact ngers 'I8 has a double bend, as illustrated, in order to increase the flexibility thereof as well as to clear the fuse tube 54 and for positioning between the arms of the clip 38. The inner ends of the contact ngers 18 are provided with outwardly extending shoulders 82 that are arranged to interflt with the inwardly extending shoulders I2 on the stationary contact clip 38. vA rivet 84 extends transversely through suitable apertures in the lingers 18 and the ends thereof are headed over to prevent movement apart of the inner ends of the contact fingers 18 beyond a predetermined distance. The rivet 84 is constructed, in accordance with the principles of prestressed contact construction set forth in the copending application hereinbefore referred to, so that the shoulders 82 are positioned slightly within the path of relative movement with the shoulders 42 on the jaws of the contact clip 38. Ifthe rivet 84 were not provided, the spring ngers 18 would move to positions apart under the influence of their inherent resiliency to such an extent that the guiding surfaces provided by the flared out ends of the Contact clip 38 would have to be much longer to bring the parts into contact engagement when the cover I2 is closed. When the rivet 84 is provided, as illustrated, it is only necessary to move the inner ends of the contact ngers 18 through a slight distance to relieve the rivet 84 and apply the force of the inherent resiliency to make a good contact engagement under relatively high pressure with the Jaws of the contact clip 88. The arms of the contact clip 88 and the outer ends of the spring fingers 18 may be flared outwardly in a downward direction, as shown in Figure 4, in order to facilitate the downward movement of the shoulders 82 and the fuse device 58 after the fusible element 58 has blown.

The interengaging shoulders 42 and 82 are provided for holding the fuse device 58 and the cover I2 in the closed position as long as the fusible element 58 remains intact. Since the contact fingers 18 are substantially in the form of straps, it is possible to have them engage the contact clip 88 with a rotary movement and then to disengage it on blowing of the fusible element 58 with a sliding movement while still maintaining contact with the clip 88 until the terminals of the fusible element 58 have been separated and the arc extinguished. Suillcient clearance is provided between the fingers 18 forming the upper contact member 16 and the shoulder 5I to permit the shoulder 82 to slide downwardly out of engagement with the inwardly extending shoulders 42 of the contact clip 88. The fuse device 58 and the cover I2 are then free to rotate about the trunnions 22. as will be readily understood.

In order to insure that the contact fingers 18 bear with equal contact pressure against both of the inner surfaces of the outwardly extending arms of the upper contact clip 88, the fuse tube 54 is arranged to be rotatable in the sleeve I9V about its longitudinal axis for a limitedextent. There will then be no tendency for a greater contact pressure to be applied to one of the contact fingers 18 than is applied to the other. Consequently each contact finger 18 will carry its share of the current and overheating of one of them will not take place.

Since it is essential that the fuse tube 54 move relative to the sleeve I9 in order to operate the lever or flipper 88a and separate the terminals of the fusible element 58, this movement must be provided for. In some cases it is undesirable to have the fuse device 58 and the'cover I2 move from the closed position on blowing of the fusible element 58. In order to prevent this movement and at the same time permit the necessary movement of the fuse tube 54 in the sleeve I9, a spacer 85, Figure 8, formed preferably of insulating material, is provided for positioning between the upper ferrule 59, as shown in Figures 2 and 6 of the drawings, and the shoulder 5I that is carried by the cover I2. In this position the spacer 85 permits the fuse tube 54 to move downwardly a suicient distance to effect the separation of the terminals of the fusible element 55. However it does not permit sufficient downward movement to cause the shoulders 82 to disengage the shoulders 42 and, consequently, the cover I2 remains closed.

In most instances it is desired to have the fuse device 58 move to such position that the shoulders 82 and 42 will be disengaged for the purpose of introducing an air gap in the circuit in addition to that which is provided by the separation 'of the terminals of the fusible element 58. Such operation is desired in order to reduce to a minimum the creepage path that would otherwise be present through the fuse device 58 and the likelihood of a flashover between the stationary terminals 82 and 88. In such case the spacer 85 may be positioned below the shoulder 5I in the position indicated by the broken lines in Figure 2 of the drawings. In this same figure the manner in which the spacer 85 prevents the downward movement of the fuse device 58 to maintain the shoulders 82 and 42 in engagement is also shown by broken lines.

Referring again to Figure 4 of the drawings, it will be observed that a roller 88 may be loosely mounted on the rivet 84 between the ends of the fingers 18 for engagement with an arcing finger 81, formed preferably of resilient material such as phosphor bronze. that is secured to the contact clip 88 under the head of the screw 48. If any arcing persists after the fusible element 58 is blown and the fingers 18 are moved out of engagement with the Jaws of the contact clip 88, it will take place between the roller 88 and the arcing finger 81, thereby avoiding pitting of the sliding contact surfaces. It will be noted that the arcing finger 81 is provided with an extension 88 that is arranged to engage the upper surface of the cap 60. This extension is provided in order to conduct readily the heat that is generated in the cap 80 and the ferrule 59 to the stationary terminal 82 but the force with which it biases the fuse device 58 downwardly is comparatively slight.

The details of construction of one of the contact fingers 18 are illustrated in Figure 9 of the drawings. As there shown the assembly comprises a resilient strip 89, formed preferably of stainless steel, and a plurality of conductor strips 90 that are formed preferably of copper. A sleeve 9| surrounds the outer ends of the spring strip 89 and the strip conductors 90 and is pressed thereon by suitable dies to the shape indicated to provide a substantially unitary construction. It will be understood that other forms of contact finger construction may be employed without departing from the scope of our invention.

The construction of the lower contact member 11 is similar to that of the upper contact member 18. As illustrated more clearly in Figure 5 of the drawings the lower contact member 11 comprises a pair of prestressed apart spring fingers 98 that are of substantially U-shaped construction the common portion of which is fiat in order to suitably engage a correspondingly flattened portion of the upper end of the sleeve I9 and screws or rivets may be provided for connection thereto. The spring fingers 98 have the double bends to increase their flexibility, as previously described. A rivet 91 loosely fits in aligned apertures adjacent the free ends of the fingers 98 and it serves to limit the movement thereof apart.

It will be observed that the extreme ends of the ngers 98 are turned inwardly and that they engage the out flared ends 45 of the lower clip 89. This construction serves to bias the sleeve I8 and the fuse device 58 and the cover I2 outwardly by reaction with the out ared ends 45 with a denite and predetermined force. This biasing force in addition to the force of gravity, when the box II is positioned in such location that it is inclined slightly from the vertical, as shown in Figure 1 of the drawings, is sufiicient to insure that the rotation of the cover I2 takes place and at the same time produces a minimum of friction between the shoulders 42 and 82 at the upper end of the fuse device 58.

In the operation of the device it will be understood that the contact member 18 serves not 2,292,341 only .to electrically connect. the fuse device 53 to the upper stationary contact clip 38 but that it alsoserves to latch it thereto. 'I'he lower contact member 11 has only a rotary movement with respect to the lower contact clip 30 and it does not move with a translatory movement as does the upper contact member 10. With the prestressed contact iinger construction a relatively high contact pressure is provided and at the same time a minimum of effort is required to move the fuse device 53 to the closed position. The prestressed contact finger construction on the movably mounted fuse device 53 permits a simplification in the design of the contact clips 38 and 38 yand provides a maximum of contact pressure with a minimum of movement being required on the part of the contact fingers of each of the contact members 16 and 11.

A modified form of contact inger construction for the upper end of the fuse tube 54 is illustrated in Figure 10 of the drawings. As there shown the fuse tube 54 is provided with a ferrule having a generally rectangular portion on the opposite sides of which flexible resilient contact fingers IOI are secured by rivets |02. Each of the contact fingers I0| comprises an outer strip |03, formed preferably of stainless steel and one or more inner strips |04 of copper to form a conducting path for the current. The outer ends of the contact fingers |03 have provided thereon sleeves I05 that are pressed thereon and to the shape indicated by suitable dies. It will be observed that the sleeves |05 forming the ends of the contact fingers |0| are provided with inner curved portions for engagement with shoulders |06 of an upper stationary contact clip |01. 'I'he contact clip |01 is secured by a screw |08 to a connector block |09 that has a transversely extending aperture ||0 therein for receiving the line conductor. The terminal connector |03 may be cementedin the box II as illustrated. The transversely extending aperture ||0 is aligned with apertures III in the sidewalls of the box for directly receiving the line conductor therein. Set screws 2 extending through the clip |01 and the connector block |00 serve to hold the line conductor in position, as will be readily understood. A bracket II3, mounted on the contact clip |01 and secured underneath the head ofthe screw |08 serves to limit the inward movement of the fuse tube 54 so that the curved portions of the sleeves |05 will be accurately positioned in contact engagement with the shoulders |06.

As long as the fusible element in the inner bore of the fuse tube 54 remains intact lthe fuse tube 54 will be held in position by the shoulders |08. The door I2 will then remain closed. However, as soon as the fusible element blows, the fuse tube I4 will slide downwardly until the shoulders |06 are disengaged, at which time the fuse tube 54 and the door |2 will swing to the open position, as previously described.

It will be understood that the contact iingers IIII are limited in their movement toward each other when out of engagement with the contact clip |01 by engagement with the inner corners of the rectangular portion |00 of the ferrule at the upper end of the fuse tube 54. I'he resilient strips |03 are initially stressed in such manner that they tend to bias the Vcontact fingers |0I inwardly beyond the movement that is permitted by the inner corners of the lrectangular portion |00. In this manner the contact fingers I0| areprestressed toward each other.

transversely therethrough.

In Figure 11 of the drawings a modified form of contact finger construction for connecting the lower endv of the fuse device to the lower stationary terminal is illustrated. As there shown the fuse tube 54 is slidably mounted in a sleeve The sleeves |20 forming the ends of the conl tact fingers I|5 engage shoulders |2| of a lower stationary contact clip |22 which may be secured by means of a screw |23 to a terminal connector |24 having an aperture |25 extending It will be observed that the aperture |25 is aligned with apertures |28 in the side walls of the box |I to readily permit insertion of the bared end of the line conductor. Set screws |21, which extend through the contact clip |22 and the connector'block |24, are-provided for securing the line conductor in position.

Since the contact ngers |I5 are biased toward each other by the spring strips ||8 and further since the sleeves |20 bear against the front side A of the shoulders |2| a denite and predetermined biasing force is constantly applied to the fuse tube 54 through the sleeve ||4 to urge it and the door I2 toward the open position. As long as. the fusible element remains intact the fuse device will remain in the closed position as held by the contact fingers |0| in engagement with the shoulders |06, Figure 10. However, as soon as the fusible element blows, this restraining action will be released and the fuse device will be moved toward the open position by the combined effects of gravity and the resiliency of the contact fingers |I8.

It will be observed that the sleeve II4 is provided with shoulders |28 on the side away from the screws IIB. These shoulders |28 serve to limit the movement of the contact fingers II8 toward each other and, since the spring strips I8 are originally so formed as to bias the contact fingers ||5 inwardly further than permitted by the shoulders |28, a prestressed construction is provided.

Since certain further changes may be made in the above constructions and different embodiments oftheinvention may be made withoutdeparting from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

We claim as our invention:

l. In a circuit interrupter. in combination, a stationary contact clip having a pair of substantially inflexible upstanding jaws, each of said jaws having inwardly extending projecting portions, a fuse device disposed to be connected to said contact clip, and a pair of prestressed apart contact iingers carried by saidfuse device and having outwardly extending projecting portions for intertting behind said projecting portions on said jaws.

2. In a circuit interrupter, in combination, a stationary contact member, a fuse device, and a. pair of prestressed contact fingers forming one Each of the terminal of said fuse device, said contact fingers being arranged and adapted to engage said stationary contact member with a substantially 1ongitudinal movement and to disengage said stationary contact member with a substantially transverse movement.

3. A circuit interrupter comprising, in combination, a support'member, a pair of spaced apart contact members carried by said support member, a fuse device adapted to receive a fuse link for bridging said contact members, means for rotatably and slidably mounting said fuse device on said support member, said fuse device being released to slide from one position to another on blowing of said fuse link, and a pair of prestressed contact fingers forming each terminal of said fuse device for individually engaging said contact members.

4. Acircuit interrupter comprising, in combination, a support member, a pair of spaced apart contact members carried by said support member, a fuse device adapted to receive a fuse link for bridging said contact members, means for rotatably and slidably mounting said fuse device on said support member, said fuse device being released to slide from one position to another on blowing of said fuse link, and a pair of prestressed contact fingers forming each terminal of said fuse device for individually engaging said contact members, said contact fingers being arranged and adapted to engage the respective contact members with a movement substantially longitudinally thereof and to disengage one of them with a movement substantially transversely thereof.

5. A circuit interrupter comprising, in combination, a support member, a pair of spaced apart contact members carried by said support member, a fuse device adapted to receive a fuse link for bridging said contact members, means for rotatably and slidably mounting said fuse device on said support member, said fuse device being released to slide from one position to another on blowing of said fuse link, a pair of prestressed contact fingers forming each terminal of said fuse device for individually engaging said contact members, and catch means interacting between one of said contact members and the corresponding pair of contact fingers for holding said fuse device against rotation, said catch means being released by the sliding of said fuse device on blowing of said fuse link.

6. A circuit interrupter comprising, in combination, a pair of contact clips disposed in insulated spaced relation each comprising a pair of substantially inexible upstanding jaws, a, fulcrum member disposed in insulated spaced relation with one of said contact clips, a fuse device adapted to receive a fuse link and rotatably and slidably mounted on said fulcrum member for bridging said contact clips, and a pair of prestressed apart plate-like contact fingers carried by and constituting one terminal member of said fuse device for engaging one of said contact clips with a rotary movement and disengaging it with a translatory movement.

7. A circuit interrupter comprising, in combination, a pair of contact clips disposed in insustressed apart plate-like contact lingers constituting the terminal members of said fuse device for4 engaging said contact clips with a rotary movement and disengaglng one of them with a translatory movement, and catch means interacting between the jaws of one of said contact clips and the contact fingers engaging therewith for holding said fuse device against rotation, said catch means being released by sliding of said fuse device on blowing of said fuse link.

8. A circuit interrupter comprising, in combination, a housing having rear, top and side walls of insulating material, a door hinged to the lower end of said housing for closing the front of the same, a fuse device adapted to receive a fuse link and slidably mounted on said door, resilient means biasing said fuse device relative to said door and restrained by said fuse link, a pair of contact members mounted on said rear wall, two pairs of prestressed plate-like contact fingers constituting the terminal members of said fuse device for engaging said contact members with a rotary movement and disengaglng one of them with a translatory movement, and catch means interacting between one of said contact members and the contact fingers engaging therewith for holding said fuse device and door against rotation, said catch means being released by sliding of said fuse device under the influence of said resilient means on blowing of said fuse link.

9. A circuit interrupter comprising, in combination, a housing having rear, top and side walls of insulating material, a door hinged to the lower end of said housing for closing the front of the same, a fuse device adapted to receive a fuse link and slidably mounted on said door, resilient means biasing said fuse device relative to said door and restrained by said fuse link, a pair of contact members mounted on said rear wall, two pairs of prestressed plate-like contact ngers constituting the terminal members of said fuse device for engaging said contact members with a rotary movement and disengaglng one of them with a translatory movement, catch means interacting between one of said contact members and the contact fingers engaging therewith for holding said fuse device and door against rotation, said catch means being released by sliding of said fuse device under the influence of said resilient means on blowing of said fuse link, and stop means interposed between said fuse device and said door whereby limited movement of the former relative to the latter is permitted on blowing of said fuse link, said limited movement being insuliicient to release said catch means.

10. A circuit interrupter comprising, in combination, a housing having rear, top and side walls of insulating material, upper and lower contact clips mounted on said rear wall and each comprising a pair of substantially inflexible upstanding jaws, a fulcrum member mounted on said rear wall below said lower contact clip, a cover for closing the front of said housing, a tubular hinge member detachably and rotatably mounted on said fulcrum member and secured to said cover, a fuse device adapted to receive a fusible element and slidably mounted in said tubular hinge member, resilient means biasing said fuse device relative to said hinge member, a lever pivoted on said hinge member, a flexible conductor extending from said fusible element and disposed to hold said lever in such position as to prevent movement of said fuse device under the influence of said resilient means, said lever acting on blowing of said fusible element to separate the terminals thereof, two pairs of prestressed apart plate-like contact fingers constituting the terminal members of said fuse device for engaging said upstanding jaws of said contact clips with a rotary movement and disengaging said upstanding jaws pf said upper contact clip with a translatory movement, and catch means interacting between said upper contact clip and the contact fingers engaging therewith for holding said fuse device and cover against rotation, said catch means being released by sliding of said fuse device under the influence of said resilient means on blowing of said fusible element.

11. A circuit interrupter comprising, in combination, a housing having rear, top and side walls of insulating material, upper and lower contact clips mounted on said rear wall and each comprising a pair of substantially inflexible upstanding jaws, a fulcrum member mounted on said rear wall below said lower contact clip, a

cover for closing the front of said housing, aA

tubular hinge member detachably and rotatably mounted on said fulcrum member and secured to said cover, a fuse device adapted to receive a fusible element and slidably mounted in said tubular hinge member, resilient means biasing said fuse device relative to said hinge member, a lever pivoted on Ysaid hinge member, a flexible conductor extending from said fusible element and disposed to hold said lever in such position as to prevent movement of said fuse device under the infiuence of said resilient means, said lever acting on blowing of said fusible element to separate the terminals thereof, two pairs of prestressed apart plate-like contact fingers constituting the terminal members of said fusel device for engaging said upstanding jaws of said contact clips with a rotary movement and disenga'ging said upstanding jaws of said upper contact clip with a translatory movement, catch means interacting between said upper contact clip and the contact fingers engaging therewith for holding said fuse device and cover against rotation, said catch means being released by sliding of said fuse device under the influence of said resilient means on blowing of said fusible element, and stop means interposed between said fus'e device and said cover whereby limited movement of the former relative to the latter is permitted on blowing of said fusible element, said limited movement being sufficient to move said lever to rapidly separate said terminals of said fusible element but insuflicient to release said catch means.

12. In a circuit interrupter, in combination, a support member, a contact clip having a pair of substantially inflexible outwardly extending jaws mounted on said support member, a fuse device slidably and rotatably mounted on said support member, said fuse device being released for sliding movement on blowing of a fusible element therein, a pair of prestressed apart contact fingers carried by said fuse device for contacty engagement with said contact clip, and interacting shoulders on said jaws and contact fingers restraining said fuse device from rotary `movement, said jaws and contact fingers being slightly inclined tothe vertical to facilitate downward movement of said fuse device on blowing of said fusible element.

13. A circuit interrupter comprising, in combination, a box open at the front, upper and lower contact clips each having' a pair of substantially inflexible outwardly extending jaws mounted on the back wall of said box, a cover hinged to the lower end of said box for closing the same, a fuse device slidably mounted on said cover and restrained from sliding by a fusible element therein, a pair of prestressed apart contact ngers constiuting the terminals of said fuse device and disposed to engage said upper and lower contact clips on rotation of said cover to close said box, and interacting shoulders on the jaws of said upper contact clip and on the contact fingers in engagement therewith restraining said cover and fuse device from rotary movement, the ends of the other pair of fingers being turned inwardly to cooperate with the jaws of said lower contact clip tov bias said fuse device and cover for rotation to the open position on disengagement of said shoulders.

14. A circuit interrupter comprising, in cornbination, a box open at the front. upper and lower contact clips each having a pair of substantially inflexible outwardly extending jaws mounted on the back wall of said box, a cover for closing the front of said box, a metallic sleeve mounted on the lower end of said cover and hinged to the lower end of said box, a pair of lower contact fingers carried by said sleeve for engaging said lower contact clip, a fuse device slidably mounted in said sleeve and restrained from movement relative thereto by a fusible clement therein, a pair of upper contact fingers carried by said fuse device for contact engagement with said upper contact clip, and interacting shoulders on the jaws of said upper contact clip and on said upper contact fingers restraining said fuse device and said cover from rotary movement.

15. A ycircuit interrupter comprising, in combination, a box open at the front, upper and lower contact clips each having a pair of substantially inflexible outwardly extending jaws mounted on the back wall of said box, a cover for closing the front of said box, a metallic sleeve mounted on the lower end of said cover and hinged to the lower end of said box, a pair of prestressed apart lower contact fingers secured to said sleeve for engaging said lower contact clip and having the ends turned inwardly to cooperate with the jaws of said lower contact clip to bias said sleeve and cover for rotation to open position, a fuse device slidably mounted in said sleeve and restrained from movement relative thereto by a fusible element therein, a pair of upper prestressed apart contact ngers carried by said fuse device for contact engagement with said upper contact clip, and interacting transverse shoulders on the jaws of said upper contact clip and on said upper contact fingers restraining said fuse device and said cover from rotary movement until after said fusible element blows.

16. In a dropout fuse device, in combination, a sleeve, a fuse tube slidably mounted in said sleeve and adapted to receive therein a fusible element having a fiexible conductor secured thereto, a lever rotatably mounted on said sleeve and normally extending substantially at right angles to the longitudinal axis of said fuse tube, said flexible conductor extending over said lever, and clamp means mounted on said sleeve to secure said flexible conductor thereto for holding said lever in its normal position so as to restrain said fuse tube against sliding in said sleeve until said fusible element blows, said lever when released on blowing of said fusible element withdrawing said fiexible conductor substantially in line with said fuse tube.

17. In a dropout fuse device, in combination, a

sleeve, a fuse tube slidably mounted in said sleeve and adapted to receive therein a fusible element having a flexible conductor secured thereto and extending out of one end of said fuse tube, a spring encircling said tube and biasing it relative to said sleeve, a lever rotatably mounted on said sleeve, an arm at said one end of said fuse tube operatively engaging said lever near its fulcrum point, said flexible conductor being positioned over said lever, and clamp means mounted on said sleeve to secure said flexible conductor thereto for holding said lever in such position as to prevent said fuse tube sliding in said sleeve under the influence of said spring until said fusible element blows.

18. In a dropout fuse device, in combination, a sleeve, a fuse tube slidably mounted in said sleeve, a fusible element fastened at one end inside of said fuse tube, 'a lever rotatably mounted on said sleeve and disposed substantially at right angles to said fuse tube and having a longitudinal groove therein on the side away from said fuse tube, an arm on said fuse tube engaging said lever adjacent its axis of rotation, a spring biasing said fuse tube relative to said sleeve, connector means carried by said sleeve, and a flexible conductor connected to the other end of said fusible element and extending outside of said fuse tube, said fiexible conductor being positioned in said groove and fastened to said connector means to hold said fuse tube against the biasing force of said spring,

19. A circuit interrupter comprising, in combination, a pair of contact clips disposed in insulated spaced relation each comprising a pair of substantially inflexible upstanding jaws, a fulcrum member disposed in insulated spaced relaton with one of said contact clips, an insulating barrier between said fulcrum member and the adjacent contact clip, a fuse-device including a fusible element rotatably and slidably mounted on said fulcrum member for bridging said contact clips, and a pair of prestressed apart platelike contact fingers carried by and constituting one terminal member of said fuse device for engaging one of said contact clips with a rotary movement and disengaging it with a translatory movement.

20. A circuit interrupter comprising, in combination, a pair of spaced apart circuit terminals, a dropout fuse device bridging said terminals, said dropout fuse device normally acting to open the circuit and to move longitudinally to an alternate position after its fusible element blows, and means for rendering said fuse device incapable of moving longitudinally to said alternate position after blowing of said fusible element.

21. A circuit interrupter comprising, in combination, a pair of spaced apart circuit terminals, a dropout fuse device bridging said terminals, said dropout fuse device normally acting to open the circuit and to move longitudinally to an alternate position after its fusible element blows, and readily detachable means cooperating with said fuse device for rendering it incapable of moving longitudinally to said alternate position after blowing of said fusible element,

22. A circuit interrupter comprising, in combination, a pair of spaced apart circuit terminals, a dropout fuse device interconnecting said terminals, said dropout fuse device normally acting to open the circuit between said terminals and being movable longitudinally to disengage at least one of them after its fusible element blows, and readily detachable means cooperating with said fuse device for rendering it incapable of disengaging said one terminal by longitudinal movement after said fusible element blows.

23. In a circuit interrupter, in combination, a terminal member having a pair of oppositely facing contact surfaces, a fusedevice including a fuse tube, and a pair of plate-lke flexible prestressed contact fingers mounted on opposite sides of said fuse tube and extending transversely therefrom for contact engagement with said contact surfaces.

24. A circuit interrupter comprising, in combination, a pair of spaced apart contact members each having oppositely facing contact surfaces; a fuse device including a fuse tube and a fusible element; and a pair of contact finger assemblies constituting the terminals of said fuse device for engaging said contact surfaces, each of said assemblies comprising a pair of plate-like contact fingers prestressed toward each other and positioned on opposite sides of said fuse tube in planes parallel to the longitudinal axis thereof and extending transversely therefrom.

25. A circuit interrupter comprising, in combination, a pair of spaced apart contact members each having oppositely facing contact surfaces, a fuse tube adapted to receive a fusible element, means for slidably and rotatably mounting said fuse tube, means restraining said fuse tube from sliding as long as said fusible element remains intact, and a pair of contact finger assemblies constituting the terminals of said fuse device for engaging said contact surfaces, each of said assemblies comprising a pair of plate-like prestressed contact fingers positioned on opposite sides of said fuse tube in planes parallel to the axis thereof and extending transversely therefrom, the contact fingers of one of said assemblies cooperating with its contact member to hold said fuse device against rotation until after said fusible element blows and the remaining contact fingers cooperating with the remaining contact member to bias said fuse device for rotation.

26. In a dropout fuse device, in combination, a sleeve, a fuse tube slidably mounted in said sleeve, a spring biasing said tube for movement relative to said sleeve, a fusible element secured in said tube, a flexible conductor fastened to said fusible element and extending outwardly of said tube, a pair of arms extending transversely from said tube at one end, a lever pivoted on said sleeve and having a portion extending between said arms toward the bore of said tube, said arms operatively engaging said lever close to its pivot axis and said lever cooperating with said flexible conductor for 4preventing said movement of said fuse tube under the influence of said spring, and flanges extending laterally from said lever into the path of said arms to insure proper positioning of said lever on re-fusing.

27. In a dropout fuse device, in combination, a sleeve, means for rotatably mounting said sleeve. a fuse tube slidably mounted in said sleeve, a spring biasing said tube for movement relative to said sleeve, said fuse tube being adapted to receive a fusi-ble element to be tensioned by said spring and restrain said tube from movement in said sleeve, and resilient latch means holding said tube and sleeve against rotation, the stress applied to said fusible element being independent of and unail'ected -by the resilient force applied to said latch means, said latch means being released after said fusible element blows and said tube slides to a predetermined position.

28. In a dropout fuse device, in combination, a

sleeve, means for rotatably mounting said sleeve, a fuse tube slidably mounted at one end in said sleeve, a spring biasing said tube for movement relative to said sleeve, said fusetube being adapted to receive a fusible element to be tensioned by said spring and restrain said tube from movement in said sleeve, a terminal carried by the other end of said tube, a stationary terminal adjacent said other end of said tube, and resilient contact means electrically interconnecting said terminals, the stress applied to said fusible element being independent of and unaffected by the resilient force applied to said contact means.

29. 4In a dropout fuse device, in combination, a sleeve, means for rotatably mounting said sleeve, a fuse tube slidably mounted at one end in said sleeve, a spring biasing said tube for movement relative to said sleeve, said fuse tube being adapted to receive a fusible element to be tensionedv by said spring and restrain 'said tube from movement in said sleeve, a terminal carried by the other end of said tube, a stationary terminal adjacent said other end of said tube, and resilient contact means electrically interconnecting said terminals and arranged and adapted to maintain substantially constant contact pressure with one of them While said tube moves through said sleeve after said fusible element blows, the stress yapplied to said fusible element being independent of and unaffected by the resilient force applied to said contact means.

30. In a -dropout fuse device, in combination, a sleeve, means for rotatably mounting said sleeve, a fuse tube slidably mounted at one end in said sleeve, a spring biasing said tube for movement relative to said sleeve, and fuse ltube being adapted to receive a fusible element to be tensioned by said spring and restrain said tube from movement in said sleeve, a terminal carried by the other end of said tube, a stationary terminal adjacent said other end of said tube, contact means electrically interconnecting said terminals with the contact engagement taking place in planes substantially parallel to the axis of said tube, and resilient means biasing said contact means into contact engagement with one of said terminals, said resilient means acting in a plane substantially at right angles to the axis of said tube whereby said fusible element is un stressed thereby.

31. A detachable contact assembly for a fuse device or the like comprising, in combination, a terminal having a transverse aperture for receiving a conductor, a contact clip having a pair of upstanding arms 'carried by said terminal and aligned with said aperture, and la substantially U-shaped resilient contact member surrounding said fuse device and constituting one terminal thereof, the ends of said contact member-being offset toward each other and biased apart for contact engagement with said arms of said con.- tact clip.

32. A circuit interrupter comprising, in combination, support means, a pair of spaced apart line terminal members carried by said support means, a fuse device adapted to receive a fusible element for bridging said terminal members, means for rotatably and slidably mounting said fuse device on said support means, lever means controlled by said fusible element for holdin-g said fuse device in the circuit closed position and adapted to release the same and lengthen the arc formed on blowing of said fusible element, contact means carried by said fuse device forming terminals for said fusible element and adapted to engage said line terminal members, said contact means being arranged and adapted to engage the respective line terminal members with a movement substantially longitudinally thereof and to disengage one of them with a movement substantially transversely thereof, and auxiliary contact means disposed to maintain circuit connection between said one line terminal member and its contact means on said fuse device while the same are being separated through a predetermined distance to prevent arcing therebetween.

33. A circuit interrupter comprising, in combination. a pair of terminal blocks positioned in insulated spaced relation and adapted to receive line conductors, a contact clip having a pair of substantially inflexible spaced apart contact jaws removably mounted on each terminal block, and a fuse device' for interconnecting the contact clips including a fuse tube, and a p'air of terminal members mounted on the side of said fuse tube remote from said contact clips and each comprising a pair of plate-like contact fingers biased in opposite directions and extending transversely alongside of said fuse tube and into individual engagement with the jaws of said contact clips.

34 A circuit interrupter comprising, in combination, a pair of terminal blocks positioned in insulated spaced relation and adapted to receive line conductors, a contact clip having a pair of substantially inflexible spaced apart contact jaws removably mounted on each terminal block, and means for interconnecting the contact clips including a longitudinally extending conducting member, and a pair of terminal members mounted on the side of said conducting member remote from said contact clips and each comprising a. pair of platelike contact fingers biased in opposite directions and extending transversely alongside of said conducting member and into individual engagement with the jaws of said contact clips.

35. In adropout fuse device, in combination, a sleeve, a fuse tube slidable in said sleeve and adapted to receive a fuse link having a ilexible lead, a lever rotatably mounted on said sleeve and normally extending substantially at right angles to the longitudinal axis of said fuse tube with the free end aligned with the bore of said fuse tube, said flexible lead being adapted to be looped over the free end of said lever but not fastened thereto, and means for anchoring said exible lead independently of said lever for holding the same in its normal position, thereby restraining said fuse tube from sliding in said sleeve until said fuse link blows.

36. The combination, in a circuit interrupter having a slidably mounted fuse tube restrained from movement by a fuse link therein having a flexible lead, of a pair of arms extending transversely from said fuse tube, a lever extending between said arms for receiving said flexible lead and having a portion engaged by said arms for preventing said fuse tube from sliding as long as said fuse link remains intact, and means on said lever cooperating With said arms for insuring proper positioning of said lever on re-fusing.

37. The combination, in ay circuit interrupter having a slidably mounted fuse tube restrained from movement by a fuse link therein having a flexible lead, of a pair of arms extending transversely from said fuse tube, and a lever having a central portion extending between said arms for receiving said flexible lea-d and oppositely extending anges adjacent its pivot axis for receiving the ends of said arms to prevent said fuse tube from sliding as long as said fuse link remains intact, said flanges having portions turned away from said arms for guiding the same onto said iianges on re-iusing.

38. A fuse construction comprising a housing having a pair of stationary contacts, a door for said housing. said door having a contact normally engaging one of said stationary contacts, a fuse tube slidably carried by the contact of said door and having a contact adjacent one end normally in engagement with the other oi' said stationary contacts, a fuse link within said fuse tube normally electrically connecting the contact of said fuse tube with the contact of said door, and means normally restraining said fuse tube against sliding motion and including fuse link extracting means carried by the contact of said door and controlled by said fuse link, said fuse link extracting means having a part located adjacent one end of said fuse tube and engaging the fuse link, and biased for motion away from and substantially in line with said fuse tube.

39. An automatic circuit interrupting switch comprising yan insulating housing having spaced contacts, a door for said housing, an arcing tube slidably supported from said door and normally heid against sliding motion, an expulsible conductor within said arcing tube normally electrically connecting said spaced contacts, means for holding said door closed irrespective of the sliding motion of said tube, mechanism for restraining said tube against sliding motion and for extracting said expulsi-ble conductor, said mechanism including a part having motion directly outwardly substantially in line with said tube, and current controlled means controlling said mechanism.

40. A dropout fuse -construction comprising, in combination. an insulating support carrying upper and lower stationary contact members, a fuse tube having upper and lower contact members for engaging said stationary contact members and being slidable relative to its lower contact member, said fuse tube being adapted to receive a replaceable fuse link having a iiexible conductor adapted to extend out of the lower end of said fuse tube, means biasing said fuse tube downwardly, means on said lower contact member for receiving and holding said flexible conductor whereby said fuse tube is restrained from said downward movement as urged by said biasing means, and a lever pivoted adjacent the lower end of said fuse tube and normally extending substantially at right angles thereto over which said exible conductor is passed, said lever belng biased downwardly away from said fuse tube for withdrawing said exible conductor therefrom on blowing of said fuse link.

4l. A dropout fuse construction comprising, in combination, an insulating support carrying upper and lower stationary contact members, a fuse tube having upper and lower contact members for engaging said stationary contact members and being slidable relative to its lower contact member, said fuse tube being adapted to receive a replaceable fuse link having a ilexible conductor adapted to extend out of the lower end of said fuse tube, means biasing said i'use tube downwardly, means on said lower contact member for receiving and holding said flexible conductor whereby said fuse tube is restrained from said downward movement as urged by said biasing means, and a lever pivoted adjacent the lower end oi' said fuse tube and normally extending substantially at right angles thereto over which said flexible conductor is passed, said lever being biased downwardly away from said fuse tube for withdrawing said exible conductor therefrom on blowing of said fuse link, the under side of said lever having a groove aligned with the bore of said fuse tube for centering said flexible conductor with respect to said bore.

ALLAN RAMSEY. SIGURD I. LINDEIL. ANTHONY VAN RYAN. 

